I love the colors in this quilt. My fantasy backing would be a beautiful ombre in those yummy blues and aquas. I tend to do patterned backings because I don't have alot of confidence in my quilting. However, I like a solid backing too because I love to see all the lovely quilting on the back.

I'd go for the second one, with the huge teal and red flowers. But there are other more "subdued" ;-) ones. Or something like that in your LQS.

I mean, you've already shown that you like teal and black on the front of the quilt. And you've got plenty of clean, straight lines in those blocks. Why repeat that on the back?

I think a quilt definitely benefits from and needs having something (totally) different on the back.

Think of the furniture in your living room. Your couch is a striped fabric. Are you also going to make the pillows from striped fabric? No, you're going to choose coordinating/complimentary colors, but in another pattern. Otherwise, it's just so bland.